This invention relates to a system for preparing highly coherent textured yarn, and more particularly, it relates to a system for preparing such yarns with pressurized fluid in a jet having a deflector arrangement at its outlet end.
It is known to overfeed one, or more, ends of continuous multifilament yarns to a jet, in which pressurized fluid, such as air, acts on the filaments to splay them, curl them into crunodal loops, and entangle the looped filaments into coherent yarn.
Fluid jet processes are also known for texturing or bulking yarn that employ both movable and fixed baffles positioned at various distances from the outlet end of the jet and at various angles to the yarn path to deflect yarn and fluid from a straight path as they leave the jet.
In making a yarn having crunodal loops, the texturing jet must forward the overfed yarn under sufficient tension to keep the yarn from wrapping on the feed rolls, and this tension is provided by the drag of the pressurized air which is moving much faster than the yarn. The air opens the yarn, whips the filaments about, forms loops in the filaments, then entangles them together into a structure which can retain the loops under the tensions which such yarns encounter when made into fabrics. The tension must be low at the jet exit to accumulate loops and form the entangled structure. Immediately thereafter, higher tension is desired to tighten the entangled structure and stabilize it.
A baffle against which the air and yarn impinge is often provided at the jet exit to provide a controlled air zone and to change the direction of yarn movement abruptly. Such baffles are especially necessary at high texturing speeds and air pressures. However, with known baffle arrangements, the air divides around the baffle, and the portion of the air which follows the yarn continues to exert tension.
Textured yarn uniformity, in terms of appearance and loop stability, is highly critical for good fabric uniformity. Since many different packages are used to make fabrics, the yarn character must be the same from one package to the next and within a package from beginning at the core to the surface, including when a package is stopped for any reason.
A texturing position stops when either a take-up package is full or the feeder yarn supply is interrupted. In other cases, the positions are stopped at the time of shift change. The stop could be initiated either automatically or manually. In either case, the electric power that drives the motor and the rolls stops. The rolls continue to turn slowly, due to the inertia, before gradually slowing down and coming to a complete stop. When the rolls are completely stopped with no yarn movement through the jet, then the air supply to the jet is stopped, either automatically or manually, usually within 1-3 seconds. Stoppage of air prior to the stoppage of the rolls would result in totally untextured yarn, since the slow forward movement of rolls will continue to feed yarn to the jet without any air to texture it.
Textured yarn manufacturers have experienced small lengths of yarn (1 to 12 inches out of total approximately 500 inches of yarn during which the rolls slowly come to a full stop) with a varying degree of fluffy and partially or poorly textured yarn character immediately prior to stoppage of the rolls. This defect is called Partially Textured Yarn Defect or PTYD. The PTYD consists of loosely bulked or fluffed yarns having insufficient filament mixing and loop interlocking so that the yarn bulk will pull out easily and will show as defects in the fabric. Although the defect is present in a majority of the commercial texturing processes, the severity of PTYD varies, depending upon actual texturing process conditions. For years, the texturizers have coped with the problem by either (A) cutting off PTYD manually prior to re-string up or (B) leaving the PTYD at the core of a new package and rejecting the "heel" as waste in subsequent process. Both solutions are inefficient, wasteful, and subject to operator judgment and error.